1. Sounds a lot like either an issue with wifi interference , or possibly a duplicate IP address issue in your local network. I’d certainly try a network refresh and see if it resolves. 
    
2. Queue limits are imposed by the ability for Sonos to download data from the streamer, who also sets a limit. You might be impacted by 1., though. I’d certainly submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

   There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

   When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

3. Not being an employee of Sonos, I can’t offer a solution here, but it would certainly be a topic of conversation when I called in to discuss the diagnostic. 

No issues with wifi.  I’m able to stream the playlist directly from Amazon Music with no issues, and no issues with my outdoor security cameras, et al.  I can stream iTunes to Sonos Roam, again with no issues.

Amazon limits the download to 500 tracks, and the original app had no problems with that. When Sonos first introduced their messy 2nd generation, I still had the original app functional on a desktop and was able to control the system from there with the complete playlist until their last update (they disabled the original app demanding an update).  So the 100 track limitation is Sonos imposed. 

Personally, I think Sonos should post the original app (with automatic updates turned off) until they can straighten out this mess.  I’d contact Sonos support, but I suspect they’re overwhelmed.  I’ll live with iTunes for the interim...